I'm trying to make a video using a greenscreen. Unfortunately I'm traveling and need to record the video outside, while not having a solid light. Ultra Key helps making most of my greenscreen transparent, but in soe parts the sun shines through, so that I would like to make them transparent manually.

In the screenshot you can see the background mostly is black as I applied Ultra Key already, but in the right side it's too bright because of the sun. Can I cut it our completely or make this part transparent all the time?